Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$133.29	8.736%	$144.9342	$144.93	$144.95	$144.90
Purchase #2	$81.69	5.612%	$86.2744	$86.27	$86.25	$86.30
Purchase #3	$47.39	3.137%	$48.8766	$48.88	$48.90	$48.90
Purchase #4	$86.95	11.289%	$96.7658	$96.77	$96.75	$96.80
Purchase #5	$235.51	8.675%	$255.9405	$255.94	$255.95	$255.90
Purchase #6	$198.61	5.530%	$209.5931	$209.59	$209.60	$209.60
Purchase #7	$218.31	11.826%	$244.1273	$244.13	$244.15	$244.10
7 purchase totals =	$1,001.75		$1,086.5119	$1,086.51	$1,086.55	$1,086.50